The use of phosphines to assist the organocatalytic β-boration reaction of α,β-unsaturated carbonyl compounds has been demonstrated with a selected number of substrates. The new method eludes the use of Brönsted bases to promote the catalytic active species and PR3 becomes essential to interact with the substrate resulting in the formation of a zwitterionic phosphonium enolate. This species can further deprotonate MeOH when B2pin2 is present forming eventually the ion pair [α-(H),β-(PR3)-ketone]+[B2pin2·MeO]â that is responsible for the catalysis.
已经证明
磷化物在对α,β-不饱和羰基化合物的有机催化β-
硼化反应中具有辅助作用,针对一组特定的底物进行了实验。这种方法避免了使用布朗斯特碱来促进催化活性物种的生成,而PR3则变得至关重要,与底物相互作用,形成一种两性离子的
磷鎓烯醇盐。这种物种在存在B2pin2的情况下可以进一步去质子化
甲醇,最终形成负责催化的离子对[α-(H), β-(PR3)-酮]+[B2pin2·MeO]-。